Applying fins to radiator tubes



Jan. 1943-. -A. o. BREDESON 2,307,355

APPLYING FINS TO RADIATOR TUBES Filed March 3, 1941 Patented Jan. 5, 1943 UNITED STATES PATENT OFFICE APPLYING FINS T RADIATOR TUBES I Albert 0. Bredeson, Minneapolis, Application March a, 1941, Serial No..38 l,508

1 Claim My present invention relates to heat exchange cylindrical fin spacing sleeves that directly contact with the tubes.

My invention involves an improved method of forming and finally adjusting the sleeves for the desired spacing action.

The invention will more fully appear in the description and consideration of the invention,

a commercial embodiment of which is illustrated in the accompanying drawing, wherein like characters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a plan or face view of a radiator fin which is shown as formed with two sleeves adapting it for application to two parallel water tubes;

Fig. 2 is a section taken on the line 2-4 of Fig. 1;

Figs. 3- and 4 are views corresponding inthe line of section to Fig. 2, but showing diflerent adjustments of the spacing sleeves;

Fig. 5 shows a plurality of spacing sleeves formed as shown in Fig. 3 applied to a water tube, said parts being shown in axial section; and

Fig. 6 is a view corresponding to Fig. 5 but showing tubes with sleeves adjusted as shown in Fig. 4 applied to a water tube.

The radiator fins are marked with the nu- H are punched in the thin sheet metal fins l0 and then, by suitable dies, the metal immediately surrounding the holes will be punched out to form cylindrical sleeves l2, as shown in Fig. 2. Then, by suitable dies or pressure devices the sleeves l2 are pressed backward through the openings in the body of the sheets so that a hub-like double fold annular rim Hat is formed,

' meral It). In forming the spacing sleeves holes as shown in Fig. 3. The extent to which the sleeve I2 will be pressed back through the hole in the fin may be varied according to the desired spacing of the fins on the tubes. In Fig. 4 the sleeve I2 is shown as pressed back completely through or into the opening of the fin perfora-,

tion so that the edge of the sleeve l2 will be flush with the face of the fin, as shown in It will now be evident that with a maximum spacing of the fins on the tubes the sleeves can be left just as shown in Fig. 2; that for closest spacing of the fins on the tubes the sleeves should be pressed back, as shown in Fig. 4; and

that for any intermediate extent of spacing of the fins on the tubes, the sleeves will be pressed back partway, more or less as shown in Fig. 3.

This variation for spacing or in the final formation or adjustment of the sleeves can be performed at any time, for instance, the fins may have their sleeves first formed as shown in Fig.

2, and subsequently, to meet the requirements for spacing, the sleeves can be pushed back more or-less to provide for such desired spacing. The

back-pressed double folds thicken up the sleeves around their tube passages so that when the fins are applied on the tubes, there will be no danger of telescoping of the sleeves and flange hubs. Fig. 5, as indicated, shows the fins with sleeves adjusted, as shown in Fig. 3,-applied on a water radiator tube l3; and Fig. 6' shows the fins with hubs adjusted, as shown in Fig. 4, applied to water tube M.

When the fins with the sleeves formed as described are applied on the tubes, there will be more or: less close contact but this contact between the tubes and the sleeves may be made more compact by slightly expanding the tubes. This expanding oi the tubes may be performed by internal pressure produced in different ways, but in Figs. 5 and 6, I have shown an expanding plunger l5 which is of slightly greater diameter than the normal interior of the tube and which may be forced through the tube to produce an expanding action. This expansion of the tube against the spacing sleeves will also slightly expand the latter and force the double fold rims l2a and/or l2b into more compact or solid contact.

In actual practice this invention has been found to be not only easily performed, but highly satisfactory for the purposes had in view,to wit: efilcient spacing action, variable spacing action, and the best kind of heat-conducting contact between the tubes and the spacing sleeves and the fins.

In carrying outthis improved process the following steps are followed; to form thefin body a relatively thin sheet of metal, preferably copper, is formed with a hole that is considerably smaller than the tube to which the fin is to be applied, and then the metal surrounding the hole is punched through to form a cylindrical Fig. 4. sleeve that is of. a diameter permitting it to be slipped onto the radiator tube or pipe. Then the sleeve is pressed back through the opening so as to form an annular double fold with an open annular space between the two folds. This operation can be readily performed by the use of dies, such as a die plate, having a passage that is slightly greater in diameter than the exterior of the spacing sleeve. Next, the fins, with the double fold sleeves, are slipped onto the radiator tube or pipe with the sleeves or hubs of the assembled fins in close spacing contact, and next and finally, the tube. with-,the applied fins, is diametrically expanded to an extent sufflcient to press the contacting sleeves outward and thereby close or force into close contact the inner and outer portions of the double folds. This expansion can be produced in difierent ways as, for example, by means of the expanding plunger i5. By these operations the contacting portions of the sleeve-like flanges are not only brought into the closest possible kind of heat conducting contact with the tube, but the double folds of the fins are pressed tightly together affording not only strong supporting hubs for the fins, but producing the best kind of heat conducting and heat radiating action.

By this improved method the last step of the process consists of expanding the tube, to which the fin has been applied, to such an extent that the sleeve, which constitutes the inner wall of the double fold, will be pressed into actual direct contact with the slightly diverging outer wall of the fold, thereby closing the diverging annular space. The importance of this is that without expanding the base of the outer wall of the fold,

the inner and outer walls of the fold are brought into solid contact thereby making the fold a substantially integral or solid heat-conducting and expansion resisting structure.

The hub-like double folds, such as shown in the drawings at Ma and l2b, not only slightly decrease the internal diameters of the inner surface of the sleeve, but widen the point of contact with the edge of the adjacent sleeve without producing any dead air space. With the sleeve extended on both sides of the fin gives a divided and more even transfer of heat through the sleeve. These improved fins can be made from any suitable metal but, in practice, we have had the best results by the use of thin sheets of aluminum or aluminum alloys. However, copper and brass are also very desirable metals for the above use. I

What I claim is:

The process of producing radiator fins and applying the same to radiator tubes which consists, first, in punching a hole in a sheet metal finforming plate, second, pressing the metal of the plate surrounding the hole, laterally to form a cylindrical sleeve, third, in pressing the sleeve backward through the plate to form a double fold hub portion, the inner and outer walls of which diverge to form an intervening annular air space, fourth, in applying said fin to a radiator tube, and fifth, expanding the radiator tube to an extent sufflcient to press the inner and outer walls of the double fold hubinto actual direct heatconducting contact and thereby closing the said diverging annular air space, without enlarging the base of the outer wall of said double fold.

ALBERT O. BREDESON 

